Flame tube for a gas turbine combustion equipment

ABSTRACT

A flame tube for gas turbine combustion equipment includes at least one wall of double-skinned construction having internal and external skins throughout the major part of its longitudinal and peripheral extent, the internal skin comprising a plurality of axially consecutive peripherally extending sections attached to the external skin at their upstream ends only and being spaced from the external skin to define respective passages therebetween, each section except the most downstream section extending downstream to the upstream end of the next section, the external skin being apertured to direct in operation jets of cooling air onto the internal skin sections for impingement cooling thereof, said cooling air thereafter flowing through said passages.

United States Patent Williamson Aug. 19, 1975 FLAME TUBE FOR A GASTURBINE 3,362,470 1/1968 Richardson 60/3965 COMBUSTION EQUIPMENT 33693632/1968 60/3965 3,384,346 5/1968 (SO/39.66 [75] Inventor: Douglas H.Williamson, Derby, 14413 6/1969 60/3965 England 3,570,241 3/1971Alexander 60/3965 [73] Assignee: The Secretary of State for Defence inHer Britannic Majestys Primary ExaminerDoug1as Hart Government f theUnited Kingdom Attorney, Agent, or Firm-Cushman, Darby & of GreatBritain and Northern Cushman Ireland, London, England 122 Filed: Nov.13, I969 1 1 ABSTRACT [2]] Appl NO; 876,504 A flame tube for gas turbinecombustion equipment includes at least one wall of double-skinnedconstruction having internal and external skins throughout the 1 1Foreign Applicafion Priority Data major part of its longitudinal andperipheral extent,

Nov. 15, 1968 United Kingdom 54398/68 the internal skin comprising aplurality of axially consecutive peripherally extending sectionsattached to [52] US. Cl, 60/39.66; 60/3965; 431/352 the external skin attheir upstream ends only and [51] Int. Cl. F02c 7/18; F23r 1/10 beingspaced from the external skin to define respec- [58] Field of Search60/3965, 39.66; 431/350, tive passages therebetween, each section exceptthe 431/351, 352 most downstream section extending downstream to theupstream end of the next section, the external skin [56] ReferencesCited being apertured to direct in operation jets of cooling UNITEDSTATES PATENTS air onto the internal skin sections for impingement2,657,531 11 1953 Pierce 60/3966 Cooling h Said Cooling air themafterflowing 2,760,335 8/1956 GOddklrd.... 60 3974 through Passages-2,919,549 1 1960 Haworth.... 60 3966 3,349,558 10/1967 Smith 60 3965 14Clams 5 Drawmg F'gures PATENTED Ans-1 9191s SHEET 1 o 3 InventorPATENTED AUB1 91975 SHEET 2 OF 3 m/FJ. II \lll/ 441 W By 0 J J WAttorneys PATENTEU 1 9 75 SHEET3UE3 Inventor Maj MM y Z Z AttorneysFLAME TUBE FOR A GAS TURBINE COMBUSTION EQUIPMENT This invention relatesto flame tubes for gas turbine engine combustion equipment.

The invention is directed to any novel feature or combination offeatures herein described and/or shown in the drawings.

Although not so restricted thereto, the invention provides in one aspecta flame tube for gas turbine combustion equipment, the flame tubeincluding at least one wall of double'skinned construction having interha] and external skins throughout the major part of its longitudinal andperipheral extent, the internal skin comprising a plurality of axiallyconsecutive peripherally extending sections attached to the externalskin at their upstream ends only and being spaced from the external skinto define respective passages therebetween, each section except the mostdownstream section extending downstream to the upstream end of the nextsection, the external skin being apertured to direct in operation jetsof cooling air onto the internal skin sections for impingement coolingthereof, said cooling air thereafter flowing through the said passages.

The passages may be open at their downstream ends to direct said flow ofcooling air across the internal surface of the flame tube wall to effectfilm cooling thereof.

There may be spacers adapted to maintain the downstream ends of the saidsections of internal skin spaced from the external skin whilstpermitting sliding movement of said downstream ends relative to theexternal skin and relative to other sections of internal skin.

Each spacer may be peripherally substantially coextensive with arespective internal skin section by which it is carried and may beapertured to permit said flow of cooling air.

Alternatively, the spacers may comprise for each said section aplurality of angularly spaced apart protuberances on a said skin whichproject towards the other said skin.

The protuberances may be blisters on the sections of internal skin,there being apertures to permit the flow of cooling air in the saidpassage to pass both internally and externally of the blisters.

The inner skin may be made of a porous material for effusion ortranspiration cooling thereof.

The external skin may comprise a plurality of axially consecutive ringsa downstream ring being of diameter such that it is disposed outwardly,with respect to the interior of the flame tube, of an immediatelyupstream ring, the downstream ring having axially aligned therewith asaid internal skin section which is attached only to the saidimmediately upstream ring.

Alternatively, the external skin may comprise a plurality of axiallyspaced rings each integrally formed and bifurcated at its downstream endto provide a respective pair of radially spaced axially extendingannular flanges, the outer flange of at least one ring, relative to theinterior of the flame tube, being attached to the upstream end of thenext downstream ring, the other flange of the at least one ring havingfixedly attached thereto the upstream end ofa said internal skinsection.

There may be radially extending flanges at the upstream end of the flametube which are adapted to support fuel injector means, said flangesbeing provided with a downstream'facing heat shield.

The flame tube may be provided at its downstream end with a dischargenozzle of double-skinned construction having internal and externalskins.

There may be apertures to permit cooling air to pass in an upstreamdirection between the internal and external skins of the dischargenozzle to effect cooling thereof and means to thereafter direct saidcooling air downstream across the internal surface of the dischargenozzle wall to effect cooling thereof.

The most downstream internal skin section of the flame tube wall mayoverlap a spigot connection between the flame tube and the dischargenozzle, to shield it from the interior of the flame tube.

The invention also provides in another aspect, to which it is notrestricted, a gas turbine engine having a flame tube as set forth above.

The invention will be described, merely by way of example, withreference to the accompanying drawings, wherein:

FIG. 1 is a longitudinal section of part of a gas turbine engine havinga flame tube according to the invention,

FIG. 2 is a similar section through a different form of flame tubeaccording to the invention,

FIG. 3 is a scrap section on line 3-3 of FIG. 2,

FIG. 4 is a view on arrow 4 of FIG. 3, and

FIG. 5 is a scrap longitudinal section of a further flame tube accordingto the invention.

Referring to FIG. 1, a gas turbine engine (not shown complete) has amain flow duct 11 in which is mounted, in axial flow series, compressormeans of which the downstream-most rotor stage 13 is shown, combustionequipment 14 and a turbine stage 16 which is drivingly connected withthe compressor 13 by means of conventional shafting (not shown). Axiallybetween the compressor stage 13 and the combustion equipment 14 there isprovided a ring of outlet guide vanes 17, and upstream of the turbinestage 16 there is provided a ring of inlet guide vanes 19.

The combustion equipment 14 comprises an annular combustion chamber 20in which is located an annular flame tube 22. In operation, compressedair from the compressor means 13 enters the combustion chamber 20, afterhaving passed through the outlet guide vanes 17, and passes into theflame tube 22 through conventional primary, secondary and tertiary airinlet chutes 21, 23 and 25 respectively. Fuel is injected into the flametube 22 in operation by one or more injector nozzles (not shown), andthe fuel and air mixture is ignited. The products of combustion leavethe flame tube 22 at its downstream and via a discharge nozzle 26 andpass to the inlet guide vanes 19 of the turbine 16. The discharge nozzle26 is connected to the flame tube via radially inner and outerstellite-coated spigot rings 26a, 26b which permit relative movement ofthe flame tube and the discharge nozzle.

During the combustion of the fuel air mixture, the flame tube walls getextremely hot, and flame tubes 22 of conventional materials have alimited life.

In order to increase the operational lifetime of a flame tube, the flametube 22 including its discharge nozzle 26 is provided with adouble-skinned construction substantially throughout its length andperiphery. The annular flame tube 22 has a radially outer wall 27 and aradially inner wall 28, each having a respective internal skin 30 and anexternal skin 32.

The upstream end of each internal skin 30 is provided with a radiallyextending flange or flanges 33 be- "arugula:

tween which may be located a fuel injector (not shown) and through whichprimary air may pass into the interior of the flame tube 22. Moreover,if desired, swirl vanes may also be mounted from the flanges 33. Adownstream-facing heat shield 33a is provided to protect the flanges33,which otherwise would be exposed to high temperatures as well as thestresses involved in supporting the injectors,

It is to be noted that the double-skinned construction of the flame tube22 extends between the radial planes of the upstream-most parts of theflanges 33 and the plane just upstream of, or substantially coplanarwith, the upstream edge of the inlet guide vanes 19.

The internal skins comprise a plurality of axially consecutive portionsthe upstream end only of each of which is attached, preferably bywelding, to the re spective external skins 32. The external skins 32each consist of two axially consecutive rings 32a, 32b, the downstreamring being of a diameter such that it is disposed outwardly with respectto the flame tube of the immediately upstream ring 32a. In thisembodiment the rings are integrally formed with each other.

There are upstream and downstream internal skin sections 35, referencedas 35a, 35b. The upstream sections 35a extend downstream to the upstreamend of the downstream section 35b. The downstream sections 35b arealigned with the downstream external skin rings 32b and are attached tothe downstream ends of the upstream rings 32a only.

The internal skin sections 35 are spaced from the external skin todefine passages 31 therebetween. In this embodiment, the spacing ismaintained at not less than a minimum amount by means of spacers 36which are carried by and are peripherally coextensive with the internalskin sections 35. Each spacer 36 is integrally formed with the skinsection 35 by which it is carried. If the spacers were not provided,there may be a tendency for one or more of the passages 31 to be closedup if the flame tube were to distort due to a hot spot therein.

The spacers 36 are not attached to the respective outer skins 32 but arefitted by an interference fit sliding joint and are provided with acoating, e.g. a plasmasprayed stellite coating. This allows relativethermal expansion between the respective inner and outer skins, andassures good resistance to frettage-wear.

The external skins 32 are provided with a large number of apertures 34which are adapted to direct a flow of cooling air so as to impinge onthe radially outer surfaces of the internal skins 30 via the passages31. The apertures 34 direct jets of cooling air onto the surface of theinternal skins 30 at a substantial angle thereto, thereby to effectimpingement cooling of the skins 30.

The spacers 36 are also provided with a number of apertures 37, 37a toallow the cooling air to pass therethrough and into the interior of theflame tube 22 from the passages 31. The apertures 37 direct cooling airemerging therefrom across and along the internal surface of the internalskin section 35b to effect film cooling thereof. Likewise, the apertures37a direct cooling air across and along the internal surface of theflame tube to effect film cooling thereof.

The external skin 32 of the discharge nozzle 26 is provided at least atits downstream end with apertures 40 which permit cooling air to passinto the passages 31 between the skins of the discharge nozzle wall toeffect cooling thereof. The apertures 40 are preferably such that saidcooling is effected at least partially by impingement cooling of theinternal skin 30.

Further apertures 42 are provided in the upstream portions of theinternal skins 30 of the discharge nozzle walls. Cooling air passes viathe apertures 42 from the passages 31 in the discharge nozzle walls intothe interior of the flame tube where it is directed by deflector plates46 to pass downstream across the internal surface of the dischargenozzle walls to effect cooling, preferably film cooling thereof,additionally to cooling which may be effected by cooling air leaving theapertures 37a.

Referring to FIG. 2, there is shown a different flame tube according tothe invention. Parts similar to those of FIG. I carry the same referencenumerals and will not be described again. Only the points of'differencewill be detailed.

The FIG. 2 embodiment differs from the FIG. 1 embodiment in that thereare three axially consecutive rings 50, 52, 54 in the radially outer andradially inner walls, each having a respective internal skin section 56,58, 60 aligned therewith. There is also an additional internal skinsection 61 at the downstream radially outer end of the flame tube.

A short length 62, 64 of both the radially outer and radially innerflame tube walls 27, 28 at the upstream ends thereof are of single-skininstead of double-skin construction, because in this version it isconsidered preferable to rely at this region on the external convectivecooling provided by the air flowing to the secondary and tertiary airchutes 23, 25 since here there is insufficient pressure differencebetween the inside and the outside of the flame tube to permit efficientimpingement cooling.

Instead of the peripherally coextensive spacers 36 there are provided aplurality of angularly spaced apart protuberances on the inner skin, inthe form of partcylindrical blisters 66, best seen in FIG. 3. Theblisters all project towards the outer skin 32, and a respectiveaperture 68 is provided in the internal skin sections immediatelyupstream of each blister to permit the flow of cooling air in thepassages 31 to pass both internally and externally of the blisters 66 tofilm-cool them. The slots bite into the adjacent blisters so that, ascan be seen from FIG. 2, the leading faces of the blisters act asscoops.

The additional internal skin section 61 is provided instead of one ofthe deflector plates 46 of the FIG. 1 embodiment. The section 61 issimilar to the sections 56, 58, 60, and not only directs the cooling airissuing from the apertures 42, but also shields the radially outerspigot ring 26b which at this part of the flame tube forms the radiallyouter external skin. A similar extra internal skin section may ifdesired be provided in place of the radially inner plate 46.

FIG. 5 shows an alternative form of the flame tube according to theinvention. The external skin 32, of which the radially outer one only isshown in FIG. 5, comprises a plurality of integrally formed (e.g.machined) rings 70, 71 each bifurcated at its downstream end to providea respective pair of axially extending radially spaced annular flanges72, 74. The outer flange 72 (relative to the interior of the flame tube)of the ring is butt-welded to a cylindrical section which itself isbutt-welded to the upstream end of the ring 71. The flanges 74 eachsupport an internal skin section 58, 60 etc., being butt-welded thereto.

In any of the described embodiments, the internal skins 30 of the flametube, including those of the discharge nozzle 26, may be made of aporous material so as to allow these skins to be effusion ortranspiration cooled in addition to the impingement cooling described sofar. Effusion or transpiration cooling may be considered to be moreefficient than merely impingement cooling because its mechanism may beseparated into two parts, namely a heat exchange between the porousmaterial and the coolant as the latter permeates through the porousmaterial, and an insulation effect which results from the mass transferacross the boundary of the material.

Preferably, most of the pressure drop across the flame tube wall isarranged to occur across the outer skin. The consequent relatively smallpressure drop across the internal skin means that pressure stresses inthe hot internal skin are much reduced or minimised. This in turnresults in an increase in the life of the flame tube, or alternativelyit allows the operating temperature of the internal skin to beincreased. It also may improve the impingement cooling efficiency.

It will be appreciated that although the invention has been describedwith reference to annular flame tubes, it is also applicable to thecan-type of flame tube.

I claim:

l. A flame tube for gas turbine combustion equipment, the flame tubeincluding at least one wall of double-skinned construction havinginternal and external skins throughout the major part of itslongitudinal and peripheral extent, the internal skin comprising aplurality of axially consecutive peripherally extending sec tions, meansattaching each section by its upstream end only to the external skin,each section being spaced from the external skin to define respectivepassages therebetween, each section except the most downstream sectionextending downstream to the upstream end of the next section, theexternal skin having apertures therein, said apertures directing jets ofcooling air onto the internal skin sections for impingement coolingthereof, the passages accommodating a flow of said cooling air which hascooled the internal skin sections.

2. A flame tube as claimed in claim 1 wherein the internal skin sectionsand the external skin define openings at the downstream ends of saidpassages, said openings directing said flow of cooling air across theinternal surface of the flame tube wall, effecting film cooling thereof.

3. A flame tube as claimed in claim 1 comprising spacers maintainingdownstream ends of the said sections of internal skin spaced from theexternal skin while permitting sliding movement of said downstream endsrelative to the external skin and relative to the other sections ofinternal skin.

4. A flame tube as claimed in claim 3 wherein each spacer isperipherally substantially coextensive with a respective internal skinsection, said respective internal skin section supporting the spacercoextensive therewith, the spacers having apertures therein permittingsaid flow of cooling air.

5. A flame tube as claimed in claim 3 wherein the spacers comprise foreach said section a plurality of angularly spaced apart protuberances ona said skin which project towards the other said skin.

ti. A flame tube as claimed in claim 5 wherein the protuberances areblisters on the sections of internal skin, the sections of internal skinhaving apertures permitting the flow of cooling air in the said passageto pass both internally and externally of the blisters.

7. A flame tube as claimed in claim 1 wherein the inner skin is made ofa porous material for effusion or transpiration cooling thereof.

8. A flame tube as claimed in claim 1 wherein the external skincomprises a plurality of axially consecutive rings, a downstream ringbeing of diameter such that it is disposed outwardly, with respect tothe interior of the flame tube, of an immediately upstream ring, a saidinternal skin section being axially aligned with the downstream ring,and having means attaching it only to the said immediately upstreamring.

9. A flame tube as claimed in claim 1 wherein the external skincomprises a plurality of axially spaced rings each integrally formed andbifurcated at its downstream end to provide a respective pair ofradially spaced axially extending annular flanges, means attaching theouter flange relative to the interior of the flame tube, of at least onering, to the upstream end of the next downstream ring, and meansattaching the other flange of the at least one ring to the upstream endof a said internal skin section.

10. A flame tube as claimed in claim 1 comprising radially extendingflanges at the upstream end of the flame tube which are adapted tosupport fuel injector means, said flanges being provided with adownstreamfacing heat shield.

11. A flame tube as claimed in claim 1 and provided at its downstreamend with a discharge nozzle of double-skinned construction havinginternal and external skins.

112. A flame tube as claimed in claim 11 wherein the discharge nozzlehas apertures to permit cooling air to pass in an upstream directionbetween the internal and external skins of the discharge nozzle,effecting cooling thereof, and means to thereafter direct said coolingair downstream across the internal surface of the discharge nozzle wall,effecting cooling thereof.

13. A flame tube as claimed in claim 11 comprising a spigot connectionbetween the flame tube and the discharge nozzle, the most downstreaminternal skin section of the flame tube wall overlapping saidconnection, shielding it from the interior of the flame tube.

14. A gas turbine comprising in flow series compressor means, combustionequipment and turbine means, the combustion equipment comprising a flametube including at least one wall of double-skinned construction havinginternal and external skins throughout the major part of itslongitudinal and peripheral extent, the internal skin comprising aplurality of axially consecutive peripherally extending sections, meansattaching each section by its upstream end only to the external skin,each section being spaced from the external skin to define respectivepassages therebetween, each sec tion except the most downstream sectionextending downstream to the upstream end of the next section, theexternal skin having apertures therein, said apertures directing jets ofcooling air onto the internal skin sections for impingement coolingthereof, the passages accommodating a flow of said cooling air which hascooled the internal skin sections.

1. A flame tube for gas turbine combustion equipment, the flame tubeincluding at least one wall of double-skinned construction havinginternal and external skins throughout the major part of itslongitudinal and peripheral extent, the internal skin comprising aplurality of axially consecutive peripherally extending sections, meansattaching each section by its upstream end only to the external skin,each section being spaced from the external skin to define respectivepassages therebetween, each section except the most downstream sectionextending downstream to the upstream end of the next section, theexternal skin having apertures therein, said apertures directing jets ofcooling air onto the internal skin sections for impingement coolingthereof, the passages accommodating a flow of said cooling air which hascooled the internal skin sections.
 2. A flame tube as claimed in claim 1wherein the internal skin sections and the external skin define openingsat the downstream ends of said passages, said openings directing saidflow of cooling air across the internal surface of the flame tube wall,effecting film cooling thereof.
 3. A flame tube as claimed in claim 1comprising spacers maintaining downstream ends of the said sections ofinternal skin spaced from the external skin while permitting slidingmovement of said downstream ends relative to the external skin andrelative to the other sections of internal skin.
 4. A flame tube asclaimed in claim 3 wherein each spacer is peripherally substantiallycoextensive with a respective internal skin section, said respectiveinternal skin section supporting the spacer coextensive therewith, thespacers having apertures therein permitting said flow of cooling air. 5.A flame tube as claimed in claim 3 wherein the spacers comprise for eachsaid section a plurality of angularly spaced apart protuberances on asaid skin which project towards the other said skin.
 6. A flame tube asclaimed in claim 5 wherein the protuberances are blisters on thesections of internal skin, the sections of internal skin havingapertures permitting the flow of cooling air in the said passage to passboth internally and externally of the blisters.
 7. A flame tube asclaimed in claim 1 wherein the inner skin is made of a porous materialfor effusion or transpiration cooling thereof.
 8. A flame tube asclaimed in claim 1 wherein the external skin comprises a plurality ofaxially consecutive rings, a downstream ring being of diameter such thatit is disposed outwardly, with respect to the interior of the flametube, of an immediately upstream ring, a said internal skin sectionbeing axially aligned with the downstream ring, and having meansattaching it only to the said immediately upstream ring.
 9. A flame tubeas claimed in claim 1 wherein the external skin comprises a plurality ofaxially spaced rings each integrally formed and bifurcated at itsdownstream end to provide a respective pair of radially spaced axiallyextending annular flanges, means attaching the outer flange relative tothe interior of the flame tube, of at least one ring, to the upstreamend of the next downstream ring, and means attaching the other flange ofthe at least one ring to the upstream end of a said internal skinsection.
 10. A flame tUbe as claimed in claim 1 comprising radiallyextending flanges at the upstream end of the flame tube which areadapted to support fuel injector means, said flanges being provided witha downstream-facing heat shield.
 11. A flame tube as claimed in claim 1and provided at its downstream end with a discharge nozzle ofdouble-skinned construction having internal and external skins.
 12. Aflame tube as claimed in claim 11 wherein the discharge nozzle hasapertures to permit cooling air to pass in an upstream direction betweenthe internal and external skins of the discharge nozzle, effectingcooling thereof, and means to thereafter direct said cooling airdownstream across the internal surface of the discharge nozzle wall,effecting cooling thereof.
 13. A flame tube as claimed in claim 11comprising a spigot connection between the flame tube and the dischargenozzle, the most downstream internal skin section of the flame tube walloverlapping said connection, shielding it from the interior of the flametube.
 14. A gas turbine comprising in flow series compressor means,combustion equipment and turbine means, the combustion equipmentcomprising a flame tube including at least one wall of double-skinnedconstruction having internal and external skins throughout the majorpart of its longitudinal and peripheral extent, the internal skincomprising a plurality of axially consecutive peripherally extendingsections, means attaching each section by its upstream end only to theexternal skin, each section being spaced from the external skin todefine respective passages therebetween, each section except the mostdownstream section extending downstream to the upstream end of the nextsection, the external skin having apertures therein, said aperturesdirecting jets of cooling air onto the internal skin sections forimpingement cooling thereof, the passages accommodating a flow of saidcooling air which has cooled the internal skin sections.